1. Field of the Invention
This invention relates to an improved tamper evident composite closure, its method of manufacturing and its method of use. More specifically, this invention provides a composite closure that is compatible with a container that lacks conventional retention structure near the opening of the container that is to be sealed.
2. Description of the Related Technology
Conventional composite closures typically include a molded plastic ring or skirt portion that is internally threaded so as to be securable onto an externally threaded portion of a container and a metallic cover or disc which is inserted into the upper portion of the ring for completing the closure. The underside of the metallic cover or disc typically has an annular groove defined therein in which a gasket material such as plastisol is positioned so that a tight seal is formed between the metallic cover or disc and the upper rim of the externally threaded portion of the container. Such conventional composite closures are typically used to seal containers made of glass or plastic that are molded to have a finish portion that is provided with external threading or other conventional retention structure. One advantage of such closures is that the skirt portion can be designed so as to be visibly tamper evident, so that the consumer is made aware if the contents of the container have been accessed after completion of the packaging process.
Within the industry, it has generally been assumed that such conventional retention structure is necessary to retain the molded plastic ring or skirt portion onto the container, and that the inclusion of the molded plastic ring or skirt portion is a practical necessity for keeping the metallic cover or disc positioned on the container for the packaging of most consumer products, especially foodstuffs. Accordingly, containers that lack such retention structure, which includes most practically available metal containers, have not generally been considered suitable for conventional composite closures. Closure assemblies are known that simply include a metallic cover or disc, which is retained on the container simply by a vacuum that is induced within the container. Such closure assemblies do not require retention structure on the container because there is no plastic ring or skirt portion. In order to open such an assembly, a consumer will either breach the seal of the cover or disc, such as by removing a plug, or pry the disc from the container with his or her fingernails or a tool in order to break the vacuum. Although such closure assemblies are appropriate for some purposes, conventional composite closures are preferred for a number of reasons, prominent among which are the factors of tamper evident construction discussed above.
A need exists for a composite closure that is compatible with a container that lacks conventional retention structure, such as external threading and that is tamper evident so that consumers will be forewarned if the closure has been previously opened.